The case control study is designed to investigate possible cause and risk factors for sarcoidosis. Evaluation of cases and controls to determine the etiology of sarcoidosis will include an inquiry into environmental and occupational exposures, family history, medical history, and collection of blood specimens. Blood specimens will be used to identify potential immunogenetic and infectious contributions to sarcoidosis by means of specialized studies involving recently developed microbiology and nucleic acid analysis techniques such as HLA Class II marker studies, mycobacterial studies, immunogenetic studies, differential display polymerase chain reactin (PCR) studies, and comparisons of nucleic acid sequences from blood specimens to those of known pathogens. Bronchoalveolar lavage studies will also be performed. Specific hypothesis to be addressed include that genetic factors, infections, and occupational or environmental factors affect risk for sarcoidosis. The clinical course study of 240 cases is designed to: (1) define sarcoidosis cases that do or do not clinically resolve over a two-year period of follow-up, and (2) develop a clinical / radiographical / physiologic sarcoidosis assessment system for reporting the severity of disease.